Problem: $ 5^{-4}$
Answer: $= \left(\dfrac{1}{5}\right)^{4}$ $= \left(\dfrac{1}{5}\right)\cdot\left(\dfrac{1}{5}\right)\cdot \left(\dfrac{1}{5}\right)\cdot \left(\dfrac{1}{5}\right)$ $= \dfrac{1}{25}\cdot\left(\dfrac{1}{5}\right)\cdot \left(\dfrac{1}{5}\right)$ $= \dfrac{1}{125}\cdot\left(\dfrac{1}{5}\right)$ $= \dfrac{1}{625}$